This invention relates to a frequency selective surface (FSS) capable of reflecting electromagnetic radiation at one frequency while transmitting radiation at another frequency and, more particularly, to a construction of such a surface by a repetitive pattern of nested sets of concentric circles and/or polygons of electrically conductive material disposed on a substrate of electromagnetically transmissive material, and to an antenna incorporating the FSS to operate at plural frequency bands.
Frequency selective surfaces have been constructed of arrays of radiating elements, or resonators, disposed on a supporting substrate of electromagnetically transmissive material. As an example of the use of such a surface, the surface may be employed in an antenna for directing radiation from two separate feeds, operating at different frequencies, to a common reflector during transmission and/or reception modes of operation of the antenna.
A problem arises in such an antenna in that the FSS is limited excessively in the amount of beam width which can be handled in the various frequency bands to be transmitted or received by the antenna. A further problem with such an antenna has been the requirement for an excessive amount of separation, in the frequency spectrum, between a band of radiation transmitted by the FSS and a band of radiation reflected by the FSS.